Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 7 15 2007 10.5194/acp-7-4149-2007 http://www.atmos-chem-phys.net/7/4149/2007/ http://www.atmos-chem-phys.net/7/4149/2007/acp-7-4149-2007.html http://www.atmos-chem-phys.net/7/4149/2007/acp-7-4149-2007.pdf 4149 4158 2007-08-07 3-D polarised simulations of space-borne passive mm/sub-mm midlatitude cirrus observations: a case study C. P. Davis cory.davis@metservice.com K. F. Evans S. A. Buehler D. L. Wu H. C. Pumphrey Institute of Atmospheric and Environmental Science, University of Edinburgh, Edinburgh, UK Dept. of Atmosphere and Oceanic Sciences, University of Colorado, Boulder, USA Department of Space Science, Lulea Technical University, Kiruna, Sweden Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA Global observations of ice clouds are needed to improve our understanding of their impact on earth's radiation balance and the water-cycle. Passive mm/sub-mm has some advantages compared to other space-borne cloud-ice remote sensing techniques. The physics of scattering makes forward radiative transfer modelling for such instruments challenging. This paper demonstrates the ability of a recently developed RT code, ARTS-MC, to accurately simulate observations of this type for a variety of viewing geometries corresponding to operational (AMSU-B, EOS-MLS) and proposed (CIWSIR) instruments. ARTS-MC employs an adjoint Monte-Carlo method, makes proper account of polarisation, and uses 3-D spherical geometry. The actual field of view characteristics for each instrument are also accounted for. A 3-D midlatitude cirrus scenario is used, which is derived from Chilbolton cloud radar data and a stochastic method for generating 3-D ice water content fields. 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